/**
 * Copyright 2013 Netflix, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.netflix.servo.monitor;

import com.google.common.util.concurrent.AtomicDouble;

/**
 * A {@link Gauge} that reports a double value.
 */
public class DoubleGauge extends NumberGauge {
    private final AtomicDouble number;

    /**
     * Create a new instance with the specified configuration.
     *
     * @param config configuration for this gauge
     */
    public DoubleGauge(MonitorConfig config) {
        super(config, new AtomicDouble(0.0));
        number = (AtomicDouble) getBackingNumber();
    }

    /**
     * Set the current value.
     */
    public void set(Double n) {
        number.set(n);
    }

    /**
     * Returns a reference to the {@link AtomicDouble}.
     */
    public AtomicDouble getNumber() {
        return number;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }

        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        DoubleGauge that = (DoubleGauge) o;

        return getConfig().equals(that.getConfig())
                && getValue().equals(that.getValue());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode() {
        int result = config.hashCode();
        final int n = Double.valueOf(number.get()).hashCode();
        result = 31 * result + n;
        return result;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Number getValue(int pollerIdx) {
        // we return the actual value at the time of the call and not a reference
        // to the atomic number so the value doesn't change and is also available to jmx viewers
        return number.get();
    }
}
